Clinical course during the 1st year after diagnosis in ulcerative colitis and Crohn's disease. Results of a large, prospective population-based study in southeastern Norway, 1990-93.

Background: The clinical course and prognosis in ulcerative colitis (UC) and Crohn's disease (CD) have been described in many studies, mostly retrospective. Such studies are hampered by problems such as inclusion over a long time period, proper definitions, incomplete case records, and outdated methods of diagnosis. In a prospective study we identified 846 patients with inflammatory bowel disease (IBD) over a 4-year period from 1990 to 1993. Uniform diagnostic and therapeutic strategies were used as a basis for later assessment of the short-term clinical course in different subgroups of UC and CD and analysis of potential risk factors for relapse or surgery.

Methods: At the time of follow-up, a mean of 16.2 months after diagnosis, 496 UC patients and 232 CD patients, altogether 98%, were available for evaluation. A colonoscopy was performed in 88% (410 of 465) of the UC patients attending a clinical examination and in 76% (164 of 216) of the CD patients.

Results: Eleven patients with UC and five patients with CD died during follow-up, four of complications related to IBD. The cumulative 1-year relapse rate in the remaining patients was 50% for UC and 47% for CD. Of the patients with relapses 11 % of the UC patients and 10% of the CD patients had a chronic relapsing course without any difference with regard to the various disease categories in UC or CD. An increased risk of relapse was found in patients less than 50 years old only in UC. In UC a higher risk for surgery was found in patients with extensive colitis compared with left-sided colitis (P = 0.011), and CD patients with small-bowel involvement had a higher risk of surgery than patients with disease confined to the colon (P = 0.021). There was no excess risk of relapse or surgery in smokers as compared with non-smokers or former smokers, nor did the risk of relapse vary with the level of cigarette consumption in either UC or CD patients.

Conclusion: The high relapse rate of around 50% for both UC and CD calls for a review of the existing treatment. Further follow-up will be necessary to improve our ability to make clinical decisions relating to medical and surgical treatment options.